1. Field of the Invention
The invention relates to a method and a machine for straightening sections using one or more straightening tools which are arranged in series above and below the material to be straightened on straightening axles which are parallel with one another, in order to eliminate multi-axle deviations from the required section.
2. Discussion of the Prior Art
After rolling, sections are fed to a cooling bed. Here they generally remain at a temperature of up to approximately 60.degree. C. for cooling purposes. As a result of the rolling process, but in particular also as a result of the cooling, the sections become distorted in a particularly asymmetrical way, both vertically and horizontally, and may additionally twist about the longitudinal axis. In addition to the geometric irregularity of the rolled material, the consequences are inherent stresses in the material which become more apparent when the section is divided.
In order to straighten elongated, cylindrical workpieces, a machine is known in which at least three straightening elements engage around the workpiece in one plane (German reference DE 196 51 422 A1). It is not possible to use this arrangement of the straightening elements in one plane to straighten sections.
Furthermore, German reference DE-AS 1264936 discloses a device for bending thin-walled sections back into the desired shape, different shaping rollers being used depending on the type of section. For sections which are bent in a U-shape, a shaping tool is known which has a disk-like tool which extends into the section. In order to be able to operate on both sides in the relatively narrow gap, the drive unit which holds the tool is mounted in a tiltable fashion. It is not possible to use this device to straighten thick-walled sections which have been produced by rolling.
Hitherto, straightening machines, in particular those which were used for relatively thick-walled sections, have been used to generate a dual-axle plane position by subjecting the section to alternating bending on certain surfaces using straightening rollers which are arranged above and below the material to be straightened and which are mounted on straightening axles or straightening disks which are each arranged in the same plane and have a preset pitch and/or a specific spacing. The alternating bending then leads ideally to an improvement in the straightness in the vertical, and possibly also, the horizontal direction.
Due to the fact that the known straightening axles are mounted at one end, the straightening axles sag during the straightening process. This causes the straightening gap between the straightening rollers to become wider in an undesired way which cannot be compensated for, said straightening rollers being attached to a shaft which ultimately results in adverse effects on the straightening result from nonuniform alternating bending, and thus nonuniform distributions of stress as well as nonuniform plastic deformations. It is to be borne in mind here that the entire amount of roll spring is made up here of deformation of the bearings, the installed elements, the upright and, in the case of electromechanical adjustment, from which the spindles and worm wheels themselves are made up. Because very different straightening forces are necessary for different sections, they will always result in different amounts of roll spring.
Because, in the case of electromechanical adjustment of the straightening axles, for example using a spindle, the straightening gap is preset without material, it is also not possible to correct the straightening gap sufficiently quickly under a straightening force. Therefore, due to the system it is not possible to compensate relatively large loads as a result of, for example, relatively large nonuniformities.
It is also impossible to use electromechanical adjustment for rapid advancing, i.e. feeding in the section with an open adjustment and subsequent closing.
In addition, it is also possible for the straightening shafts to be overloaded, resulting in a fracture, if an excessively high adjustment value has been selected.
By constructing the straightening rollers from disks it is possible to influence the section in a selective fashion, enabling the dimensions to be set accurately. Because the nonuniformities may be manifest in different ways over the length of the section, additional variable forces are produced, which, as illustrated above, also affect the sagging of the straightening axles.